Hydrostatic transmission

Abstract

An improved compact design for a hydrostatic transmission having a hydraulic pump and hydraulic motor mounted on a center section in a housing, wherein the pump and motor are mounted at generally right angles to one another, and the longitudinal axis of the input shaft is located between a first and second parallel planes located at respective ends of the motor shaft and the longitudinal axis of the motor shaft is located between a third and fourth parallel planes located at respective ends of the pump shaft.

1. A hydrostatic transmission comprising:
 a hydraulic pump driven by a pump shaft and a hydraulic motor engaged to and driving a motor shaft, wherein the pump and motor are mounted in a sump;  
 a center section mounted in the sump and supporting the hydraulic pump and hydraulic motor, the center section comprising: 
 a pump running surface having a first opening formed therein to receive the pump shaft;  
 a first structure extending upward from and generally perpendicular to the pump running surface and comprising a second opening extending generally parallel to the pump running surface; and  
 a second structure extending upward from and generally perpendicular to the pump running surface and comprising a third opening extending generally parallel to the pump running surface.  
 
 
   
   
     2. The hydrostatic transmission of  claim 1 , wherein the first structure further comprises a motor running surface for supporting the hydraulic motor. 
   
   
     3. The hydrostatic transmission of  claim 1 , wherein the first opening extends through the first structure. 
   
   
     4. The hydrostatic transmission of  claim 3 , wherein the second opening supports the motor shaft. 
   
   
     5. The hydrostatic transmission of  claim 4 , wherein the pump shaft and motor shaft overlap when viewing the center section along a line of sight parallel to the pump running surface and between the first structure and the second structure. 
   
   
     6. The hydrostatic transmission of  claim 4 , further comprising a bearing positioned within the second opening. 
   
   
     7. The hydrostatic transmission of  claim 1 , wherein the third opening extends through the second structure. 
   
   
     8. The hydrostatic transmission of  claim 1 , wherein the first opening and the second opening are co-linear. 
   
   
     9. The hydrostatic transmission of  claim 1 , wherein the first structure and the second structure are positioned on generally opposite sides of the center section. 
   
   
     10. A center section for a hydrostatic transmission comprising:
 a pump running surface for a hydraulic pump;  
 a first structure extending upward from and generally perpendicular to the pump running surface and defining a first plane, the first structure having a first opening formed therein parallel to the pump running surface;  
 a second structure extending upward from and generally perpendicular to the pump running surface and defining a second plane, the second structure having a second opening formed therein parallel to the pump running surface; and  
 wherein the pump running surface is positioned between the first plane and the second plane.  
 
   
   
     11. The center section of  claim 10 , wherein the first structure further comprises a motor running surface for a hydraulic motor. 
   
   
     12. The center section of  claim 11 , wherein the first opening extends through the first structure. 
   
   
     13. The center section of  claim 12 , wherein the opening in the first structure supports a motor output shaft. 
   
   
     14. The center section of  claim 13 , further comprising a bearing positioned within the first opening. 
   
   
     15. The center section of  claim 10 , further comprising a third opening formed on the pump running surface to support a pump input shaft. 
   
   
     16. The center section of  claim 10 , wherein the second opening extends through the second structure. 
   
   
     17. The center section of  claim 10 , wherein the first structure is integrally formed as part of the center section. 
   
   
     18. The center section of  claim 17 , wherein the second structure is integrally formed as part of the center section. 
   
   
     19. A center section for a hydrostatic transmission comprising:
 a pump running surface comprising an opening;  
 a plurality of attachment openings formed in the center section and extending generally perpendicular to the pump running surface;  
 a first structure extending upward from and generally perpendicular to the pump running surface and comprising a first opening extending generally parallel to the pump running surface; and  
 a second structure extending upward from and generally perpendicular to the pump running surface and comprising a second opening extending generally parallel to the pump running surface, wherein the first opening and the second opening are generally co-linear.  
 
   
   
     20. An axle driving unit, comprising:
 a housing forming a sump;  
 an axle disposed in the sump;  
 a center section separably attached to the housing and disposed in the sump, the center section having a pump mounting surface and a motor mounting surface;  
 a hydraulic pump mounted on the pump mounting surface in the housing, wherein a rotary axis of the hydraulic pump is disposed perpendicular to the axle;  
 an input shaft disposed on the rotary axis of the hydraulic pump;  
 a hydraulic motor mounted on the motor mounting surface in the housing so as to be fluidly connected to the hydraulic pump, wherein a rotary axis of the hydraulic motor is disposed parallel to the axle;  
 an output shaft disposed on the rotary axis of the hydraulic motor and drivingly connected to the axle, the output shaft having a first end portion connected to the hydraulic motor, and a second end portion extended oppositely to the hydraulic motor through the center section; and  
 an output gear disposed on the output shaft so as to drivingly connect the output shaft to the axle.  
 
   
   
     21. The axle driving unit of  claim 20 , further comprising a brake rotor disposed on the second end portion of the output shaft. 
   
   
     22. The axle driving unit of  claim 21 , wherein the brake rotor is disposed outside of the sump.